Bug ID 860005: Ephemeral nodes/pool members may be created for wrong FQDN name

Last Modified: Sep 13, 2023

Affected Product(s):
BIG-IP LTM(all modules)

Known Affected Versions:,,,,, 12.1.4,, 12.1.5,, 13.0.0, 13.0.0 HF1, 13.0.0 HF2, 13.0.0 HF3, 13.0.1, 13.1.0,,,,,,,,, 13.1.1,,,,, 13.1.3,,,,,, 14.0.0,,,,,, 14.0.1,, 14.1.0,,,,,, 14.1.2,,,,,,,,, 14.1.3, 15.0.0, 15.0.1,,,,, 15.1.0,,,,,, 15.1.1

Fixed In:
16.0.0, 15.1.2,,,

Opened: Dec 11, 2019

Severity: 3-Major


Under rare timing conditions, one or more ephemeral nodes and pool members may be created for the wrong FQDN name, resulting in one or more ephemeral pool members being created incorrectly for a given pool.


When this issue occurs, traffic may be load-balanced to the wrong members for a given pool.


This problem occurs when a DNS Request is sent to resolve a particular FQDN name with the same DNS Transaction ID (TXID) as another DNS Request currently pending with the same DNS name server. When this occurs, the IP addresses returned in the first DNS Response received with that TXID may be incorrectly associated with a pending DNS Request with the same TXID, but for a different FQDN name which does not actually resolve to those IP addresses. The timing conditions that produce such duplicate TXIDs may be produced by one or more of the following factors: 1. Many FQDN names to be resolved. 2. Short DNS query interval values configured for the FQDN template nodes (or short TTL values returned by the DNS name server with the query interval configured as 'ttl'). 3. Delayed responses from the DNS name server causing DNS queries to remain pending for several seconds.


It may be possible to mitigate this issue by one or more of the following actions: -- Ensuring that the DNS servers used to resolve FQDN node names have sufficient resources to respond quickly to DNS requests. -- Reducing the number of FQDN template nodes (FQDN names to be resolved). -- Reducing the frequency of DNS queries to resolve FQDN node names (FQDN names) by either increasing the 'interval' value configured for FQDN template nodes, or by increasing the TTL values for DNS zone records for FQDN names for FQDN nodes configured with an 'interval' value of 'ttl'.

Fix Information


Behavior Change

Guides & references

K10134038: F5 Bug Tracker Filter Names and Tips